The content block widget in Feather uses the Kendo editor (link). It enables you to specify which tools are available in the editor toolbar. The Feather’s Content block leverages this and sets a predefined list of tools.

You can change the Content Block toolbar globally (for the default Feather Content Block widget) by replacing the default view that Feather uses. You need to create a folder structure in your Sitefinity web application on root level with path client-components\fields\html-field and inside of it create a file named sf-html-field.sf-cshtml. This way you override the default view for the html field which is used by the Feather Content Block widget designer. The default file content is here. As you can see all of the available tools are listed in the k-tools attribute value.

In order to remove the Bold button, we only need to delete the "bold" tool. The resulting file is here and you should have the same folder structure as in this repository.

To run this sample, get the sf-html-field.sf-cshtml file from this SitefinityWebApp/client-components/fields/html-field folder in this repository and place it in client-components\fields\html-field folder of your Sitefinity web application.